1. Field of the Invention
The present invention relates to an ink back flow preventive for water-based ball-point pens and water-based ball-point pens provided with said ink backflow preventive.
2. Description of the Prior Art
Compared with an ink for oil-based ball-point pens of similar forms, an ink for water-based ball-point pens has lower viscosity. Therefore, a backflow preventive is provided in an ink containment tube opposite to a pen tip for the prevention of ink flowage.
The examined Japanese Patent Laid-Open publication No. 3016749 (patent document 1) shows that with a composition of compounding styrene-based thermoplastic elastomer in ambient temperature liquid-like hydrocarbon, all the performance required for a backflow preventive can be satisfied which includes not only prevention of ink flowage, but also preferable impact resistance, no oil separation, preferable followability, no thin spot of the ink, and no dripping or side leaking.
In the unexamined Japanese Patent Laid-Open publication No. 2001-353993 (patent document 2), although the object of this invention is to control rheology, with the similar composition to the examined Japanese Patent Laid-Open publication No. 3016749, a backflow preventive is provided with stable followability not depending on writing flow rate and writing speed.
However, when such a backflow preventive for water-based ball-point pens with large amount of ink consumption is used, following gets difficult in the midway of writing, thereby causing some broken written lines. Further, depending on the case, a whole back flow preventive gets deformed since only one part of the back flow preventive attempts to follow, causing gaps with an ink containment tube and therefore, ink flowage may occur from the rear end of a containment tube when a pen tip is directed upward.
In many cases, these phenomena get remarkable when exposed to under high temperature of about 50, and this is assumed to be that a back flow preventive which contains styrene-based thermoplastic elastomer tend to show remarkably strong rubber elasticity and together with adhesive property that styrene-based thermoplastic elastomer has, thereby showing the tendency of temporarily adhering to an ink containment tube.
The object of the present invention is to solve the above mentioned problems, to provide a backflow preventive hard to be deformed by itself in any case, with stable followability, and capable of securing an ink flow even when exposed to high temperature environment, and to provide a water-based ball-point pen provided therewith.